Battery packs have already been used in a wide variety of portable devices, such as portable telephones, digital still cameras, portable game machines, notebook personal computers, and electric tools. Today, battery packs are being used not only in the above mentioned devices but also in the fields that require higher power outputs and higher capacities, such as power-assisted bicycles and electric vehicles, and household electric storage devices.
One of the types of secondary battery cells that are currently the most often used in battery packs is lithium-ion secondary battery cell. A lithium-ion secondary battery cell has many advantageous features, such as being able to tolerate repetitive use, having high-voltage power outputs, having a high energy density, having a low self-discharge rate, and having a long life. Because of such advantageous features, lithium-ion secondary battery cells are being in a very wide variety of fields. Meanwhile, to satisfy the demand for higher-output and higher-capacity devices, secondary battery cells (single cells) are now often used in the form of an assembled battery, as a large number of cells are connected in series or in parallel. Such a method of use, though having great advantages, involves a very large amount of energy, and therefore, requires handling with greater care.
To determine whether battery packs mounted on electric power consumption devices can be used safely for the electric power consumption devices, many battery authentication systems have been introduced to authenticate the secondary battery cells provided in the battery packs. A technique of reading individual authentication information such as ID numbers from secondary battery cells each having a wireless IC tag (an integrated circuit) has been known from Japanese Patent Application Laid-Open No. 2006-236806, for example.